Abstract:

In this paper, Lactobacillus casei, L. brevis, L. acidophilus, L. plantarum, L. rhamnosus and L. bulgaricus were
individually used to ferment soymilk. Changes in pH, titratable acidity and free amino nitrogen during fermentation were
determined. The viable counts of bacteria, texture parameters and sensory evaluation of soymilk fermented by lactic acid
bacteria were measured. The results showed that pH values of the soymilk fermented by the first five strains were decreased
significantly during the fermentation. However, pH of L. bulgaricus was decreased slowly and reached 5.2 at 24 h of
fermentation. Viable counts of the soymilk fermented by these six strains reached more than 1.0×108 CFU/mL. Texture
analysis showed that the stability, consistency, viscosity, and adhesion index of the soymilk yoghurt produced with L. casei,
L. brevis, L. acidophilus and L. plantarum were higher. Sensory evaluation results indicated that the fermented soymilk
produced with these four strains had higher scores and could be accepted by consumers easily. Thus, these four strains could
be suitable for the production of fermented soymilk products.

Key words: lactic acid bacteria, soymilk, fermentation characteristics